A deposit of $50 is placed in a savings account. Each month, the amount deposited is tripled. Write the function that models the exponential change between the number of months, [tex]\( t \)[/tex], and the amount of money deposited in the savings account, [tex]\( a(t) \)[/tex].

A. [tex]\( a(t) = 50 \cdot \left(\frac{1}{3}\right)^t \)[/tex]

B. [tex]\( a(t) = \frac{1}{3} \cdot 50^t \)[/tex]

C. [tex]\( a(t) = 3 \cdot 50^t \)[/tex]

D. [tex]\( a(t) = 50 \cdot 3^t \)[/tex]



Answer :

Let's determine the correct function that models the exponential change between the number of months, [tex]\( t \)[/tex], and the amount of money deposited in the savings account, [tex]\( a(t) \)[/tex].

We know the following:
- The initial deposit is [tex]\( \$50 \)[/tex].
- The amount of money in the account triples each month.

Given this information, we need an exponential function that represents the amount of money after [tex]\( t \)[/tex] months. In general, an exponential growth function can be written as:

[tex]\[ a(t) = P \cdot r^t \][/tex]

where:
- [tex]\( P \)[/tex] is the initial amount (in this case, \[tex]$50), - \( r \) is the growth rate (in this case, the amount triples, so \( r = 3 \)). Now, substituting these values into the general form of the exponential function: \[ a(t) = 50 \cdot 3^t \] So, the correct function that models the growth of the savings account is: \[ a(t) = 50 \cdot 3^t \] Thus, the correct choice is: \[ a(t) = 50 \cdot 3^t \] If we want to know the amount in the account after 2 months, we substitute \( t = 2 \) into the function: \[ a(2) = 50 \cdot 3^2 = 50 \cdot 9 = 450 \] After 2 months, the amount in the savings account will be \$[/tex]450.

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